Added JsonMessage to the control channel.

remoting/client/client_user_interface.h

Index: remoting/client/client_user_interface.h
diff --git a/remoting/client/client_user_interface.h b/remoting/client/client_user_interface.h
index 9779835cc97154fd83b86e08a97c81b30e5b1822..88d3e796991581b435cd447c11ece8d108bc6f11 100644
--- a/remoting/client/client_user_interface.h
+++ b/remoting/client/client_user_interface.h
@@ -42,6 +42,10 @@ class ClientUserInterface {
   virtual void SetPairingResponse(
       const protocol::PairingResponse& pairing_response) = 0;
 
+  // Deliver an extension message from the host to the client.
+  virtual void DeliverHostMessage(
+      const protocol::ExtensionMessage& message) = 0;
+
   // Get the view's ClipboardStub implementation.
   virtual protocol::ClipboardStub* GetClipboardStub() = 0;